 |
| How soon are the OTC pregnancy tests positive and when should you take one? |
|
 |
|
Pregnancy tests that are OTC (Over the Counter) involve testing a first
morning (the most concentrated because you haven't been drinking overnite) urine
specimen and test for HCG (human chorionic gonadotropin).
HCG is only produced by a pregnancy once the embryo
implants (in the uterus in a normal pregnancy, and elsewhere in an
abnormal place as in an ectopic pregnancy).
Many women who are trying to become pregnant are so excited at the prospect of
pregnancy and can't wait to find out if they are successful.
They track ovulation and then want to know when they can find out.
The sperm meets the egg in the fallopian tube and forms an embryo, and
then the embryo takes the journey over about a week down the
tube and into the uterus where it implants.
Once implantation happens, then HCG is secreted and the woman can
be tested for pregnancy. HCG is secreted 8-10 days after ovulation,
and at this time the level is very low. Blood HCG testing can
detect tiny amounts of HCG as low as 5IU/L (anything greater than
5 is considered positive).
In urine, however, HCG cannot be detected until it reaches a level
of 20-25 IU/L in most OTC tests. You would expect a level of
about 50 IU/L at the time of the missed menstrual period.
Therefore, the day or two before, or the day of the missed menstrual
cycle one would expect to see a positive OTC test.
Women with histories of ectopic pregnancies, or who have risk factors
for an ectopic should be tested ASAP after a period is missed
by blood in the doctor's office, and should not rely on OTC testing.
Women who are not at high risk should wait for the missed period to
test OTC (testing too early can lead to false negatives, where you
really are pregnant but the test tells you that you're not) unless
otherwise specified by their physician.
|
Wendy Fried, M.D., FACOG, FACS, is an OB/Gyn with Northern Obstetrics and Gynecology, PC in North Hills, New York
|
|
|
|
